The invention relates to improvements in disc-shaped bodies which can be used with advantage as components of clutch plates, e.g., in friction clutches of motor vehicles. More particularly, the invention relates to improvements in disc-shaped bodies which can be used for transmission of torque between rotary driven and driving parts, e.g., between a flywheel and/or a pressure plate on the one hand and the input shaft of a change-speed transmission on the other hand.
A clutch plate normally comprises a hub having (a) an internally splined sleeve which can be slipped onto the input shaft of a change-speed transmission and (b) a flange which surrounds and can (but need not) be an integral part of the sleeve. The clutch plate further comprises a carrier of friction linings and frequently a set of energy storing elements in the form of coil springs which are interposed between the flange and the carrier and resist rotation of the carrier relative to the flange and/or vice versa. The friction linings are disposed between the flywheel and the pressure plate of a friction clutch to rotate the hub (and hence the input shaft of the transmission) when the engine is on to drive the flywheel and the cutch is engaged (i.e., when the pressure plate urges the friction linings against the flywheel). Similar clutch plates can be used in other parts of power trains in motor vehicles, e.g., in a bypass (lock-up) clutch which is used in conjunction with a torque converter.
In order to avoid rapid or excessive wear as well as to reduce the likelihood of frictional corrosion of teeth or splines which transmit torque between the sleeve of the hub and a shaft, it was already proposed to provide the entire hub of the clutch plate with a coat of nickel. As a rule, the procedure involves a so-called currentless application of nickel. Certain presently preferred techniques include the BLASBERG (trademark) process, the DURNICOAT (trademark) process and the KANIGEN (trademark) process. As a rule, the thickness of the applied coat of nickel is in the range of 30.mu..